HQV 4 1899 



STRUCTURE OP THE LARVA OF SPONGILLA LACUSTRIS. 363 



^^ 



The Structure and Metamorphosis of the Larva 

 of Spongilla lacustris. 



By 



Richard Evans, B.A., 



Of Jesus College, Oxford. 



With Plates 35—41. 



[This memoir was awarded the " Rolleston Memorial Prize " of the 

 University of Oxford for the year 1898.— E. R. L.] 



Contents. 



PAGE 



I. Introduction ....... 364 



A. Historical review ..... 364 



B. Summary of the author's results . . . 367 



(a) Histology of the larva . . . 367 



(b) Metamorphosis and subsequent development . 370 



II. Detailed Account of the Development . . . 374 



A. Histology of the larva ..... 374 



(a) Flagellated cells . . . .376 



(b) Inner mass ..... 378 



Characters of inner mass in type A . 383 



» B . 384 



„ J, „ C . 385 



„ B . 390 



B. The fixation, metamorphosis, and further development . 394 



(a) Features common to the metamorphosis of all 



larvae . . . .398 



(b) Special features of the metamorphosis . 408 



(1) Of type C . . . .409 



(2) Of type D . . . .415 

 (<?) Further remarks on the formation of the general 



canal system . . .418 



VOL. 42j PART 4. NEW SERIES. C C 



